Wireless communication devices often require multi-band antennas for transmitting and receiving radio communication signals often called Radio Frequency (RF) signals. When such wireless communication devices are roaming they may need to selectively register and communicated on multi-band frequencies. For example, in specific locations, some network operators may provide one or more systems for communicating with these wireless communications devices, some of these systems are typically: a) a GSM system operating in a 880 to 960 MHz frequency band; b) a UMTS system operating in a 2,110 to 2,170 MHz frequency band; and c) a DCS system operating in a 1710 to 1800 MHz frequency band. Also, wireless communication devices may require to use Bluetooth™ frequencies operating in a 2,400 to 2,484 MHz frequency band. It will also be understood that further frequency bands, such as GPS frequency bands, may be required to be used by wireless communication devices.
Current consumer requirements are for compact wireless communication devices, such as cellular or radio telephones, that typically have an internal antenna radiator element instead of an antenna stub that is visible to the user. Furthermore, there has also been a recent trend towards thin form factor cellular telephones. These thin form factor cellular telephones require a miniaturized internal antenna radiator assembly comprising an internal antenna radiator element coupled to a ground plane, the ground planes being typically formed on or in a circuit board of the telephone. Further, these internal antenna radiator elements such as a Planar Inverted F Antenna (PIFA) or Planar Inverted L Antenna (PILA) are considered advantageous in several ways because of their compact lightweight structure, which is relatively easy to fabricate and produce.
Internal antenna radiator assemblies are typically installed inside a cellular telephone where congested conductive and “lossy” components are placed nearby. The internal antenna radiator assemblies must therefore preferably be able to cover multiple frequency bands to, for instance, accommodate two or more of the 880 to 960 MHz, 2,110 to 2,170 MHz, 1710 to 1800 MHz, 2,400 to 2,484 MHz frequency bands whilst not being the deciding factor that limits the desired thin form factor of the cellular or radio telephone.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.